GPT-5.6 Luna vs. GPT-6 Astra: Is a $1.20 Model Good Enough for Code Review?

GPT-5.6 Luna costs $0.20 per million input tokens and $1.20 per million output tokens; GPT-6 Astra costs $10 per million input tokens and $50 per million output tokens. In a 50-pull-request benchmark, Luna identified 69 bugs for $0.20, while Astra found 92 bugs for $5.66. Luna generated 3.1× more output tokens per review and completed each review in 23 seconds, compared to Astra’s 36 seconds. Luna’s precision was 25% incorrect comments, whereas Astra’s error rate was 4%. The cost per bug for Luna was $0.20, 28 times lower than Astra’s $5.66.